Bit of a dilemma, hoping for some advice. (cross posting in general bonvoy london thread)

Scenario: me and 2 other guys (late 20s, all good friends) need 1 night in London. I'm trying to use my 40k free night cert. Friday night in March 2020. Titanium status. 2 of the guys don't mind sharing a queen size or above bed.

At the Bankside Hotel, there's availability for Generous Guest Room, 2 queen, 40K points + 100 GBP. However, tried to book this and the agent says the certificate can't be used for a "premium" room. Has to be used for rooms that are 40K points only, and not additional $.

At the Bankside, I could book modest guest room (1 king) for 40K, using the certificate...and hope for an upgrade. Anyone have a sense of the upgrade probability at this property, Friday night in March? There seem to be both 1 king + sofa bed rooms, and 2 queen rooms that would in theory be available. If an upgrade didn't come through, would kind of be screwed.

Not against any of the properties in London where I could use my 40k cert, but it's almost impossible to find 2 queen beds (or King + sofa bed) based on my search.